Fig. S1. Frequency of CD4+CD25highCD127low T cells in uraemic patients. The black cells in the bivariate dot-plots represent the CD4+CD25highCD127low T cells in the uraemic patients included in this study. The frequency ranged from 2·2 to 6·7% of the total number of CD4+ T cells. The visual intensity of the black cell population varies because different number of events were recorded in each plot.


Fig. S2. Phenotype of mature dendritic cells (mDC) and DC-10. The phenotypes of mDC (green) and DC-10 (red) were determined by staining for CD1a, CD14, CD40 and CD86. Clearly, mDC are positive for CD1a, CD40 and CD86 and negative for CD14. In contrast, DC-10 are negative for CD1a and positive for CD14, CD40 and CD86 (being less positive for CD86 than mDC). Unstained controls are shown in black. The figure depicts one representative example of monocytes from a healthy blood donor that have been differentiated into mDC and DC-10.


Fig. S3. Expansion of CD4+CD25highCD127low T cells using dendritic cells (DCs). (A) Expanding clusters of T cells started to appear after 2–3 days and were located mainly in the periphery of the round bottom plates. Initially, these clusters were adherent to the bottom of the plate, but as expansions progressed the clusters detached. (B) Upon closer visualization, T cells were clustering around individual DCs. Here, a representative expansion with mature DC is shown.


Fig. S4. Purity of expanded Treg preparations from uraemic patients and healthy blood donors. Regulatory T cells (Tregs) from uraemic patients and healthy controls were sorted by fluorescence activated cell sorting (FACS) and expanded subsequently with mature dendritic cells (mDC) as feeder cells for 2–3 weeks. Next, the cells were rested overnight and assessed for a CD4+CD25highforkhead box protein 3 (FoxP3)+ phenotype (Treg phenotype). The results show that mDC-expanded Treg preparations from healthy blood donors have a higher purity (92·6%) compared to Treg preparations from uraemic patients (72·0%, P = 0·0051).

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